FIF Supports Research into the Impact of a Genetic Bottleneck on Island Foxes

When a population declines to a small number of survivors and then increases dramatically over the next few generations, there are always questions about genetic issues.

Meet Elisabeth Leung a student at the University of California at Riverside. Working with her advisor Professor Ellie Armstrong, Leung is “Exploring founder contributions from the captive island fox breeding programs for Santa Rosa and San Miguel Island using genomic sequencing.”

FIF is supporting Leung’s research because she is delving into an important question with long-lasting consequences for island foxes.

 

Around 26 years ago, the island fox populations on Santa Rosa and San Miguel Islands dropped to a critically low number: 15 surviving individuals on each island. When we look at Santa Rosa’s estimated population of 2,536 island foxes in 2023, all of them have descend from just 12 individuals in captive breeding: 4 males and 8 females.

Elisabeth Leung’s investigation will look directly at the genetics of the original founding individuals on Santa Rosa Island and San Miguel Island and compare their DNA to their descendants on the islands today.

 

Why is this important? Typically a population has some members with genetic-related health issues, maybe a tendency toward heart problems, a physical deformity, or an increased occurrence of specific cancers. Usually, these individuals are a small minority in the population because they are less successful passing on their genes before they die. When survivors are randomly chosen, rather than because they have traits that drive their success, traits that are not necessarily beneficial can increase across a population; this is called “genetic drift.”

With just 4 males contributing to the first generation of captive-born island foxes on Santa Rosa Island, if just one of those males carried a gene that increased health risks, a greater percentage of the population could be impacted. The recovered population might then have higher numbers of individuals with non-beneficial genetic traits. Overtime this would be expected to cause “inbreeding depression”–a magnification of negative traits and reduction in species vigor.

The Florida panther (Puma councilor coryi) is a well-known example of “inbreeding depression.” Genetic problems arose as the population became very small, leading to reduced male fertility and noticeably kinked tails. The inflammation response of Santa Catalina Island foxes to ear mite infestation may be linked to genetics or epigenetics and is currently being investigated by Alexandria DeCandia at the Smithsonian.

biologist examines island fox ear during health check

Though geneticists have raised concerns about island foxes, there is no evidence of current genetic problems.

Today genetic research can delve deeper into DNA and health-related issues than it could 26 years ago. See FIF Grant for Transcriptomic Research

Leung’s research will help us understand the evolutionary impact of recovering from a small founding population. Has there been genetic drift in the fox populations on these two islands? What has changed or not changed in island fox genes?

To examine these changes, the lab at UC Riverside is also creating the first island fox reference genome. The island fox pictured here is fox “25205” on Santa Rosa Island. Blood samples from this island fox will be used to assemble the first complete island fox genome.

Genetic research has entered a golden age and donors like you are helping uncover important genetic information to help island foxes survive into the future.

FIF 2024 Research Grant Investigating Link Between Island Fox Genetics and Health

Meet Kimberly Schoenberger, recipient of FIF’s 2024 Island Fox Research Grant and a PhD candidate at the University of Southern California (USC) Dornsife College of Marine and Environmental Biology.

Schoenberger is initiating the first investigation of island fox genetics using transcriptomics. This leading-edge research uses RNA (the copier of DNA) to look at a species’ genetic material and evaluate it for protein production and vital cell functions. Transcriptomics provides insight into how genes turn on or off in cells and how this may influence health or disease.

 

The project will analyze three important aspects of island fox genetic expression: 1) what are the genetic differences between the six island fox subspecies; 2) how do different environmental conditions and demographics impact gene expression; and 3) will identify genes that are being influenced by disease or parasite exposure.

(As Catalina Island foxes were recovering from a severe population low, they experienced high levels of cancer due to an extreme immune system response to ear mites. This condition does not occur on other islands. Dr. A. DeCandia’s microbiome investigation identified a connection with specific bacteria (elaborated on by Jasmine Lu paper). Husbandry efforts currently control the ear mites, but the epigenetic link between the inflammation and eventual cancer remains unknown.)

Disease and parasites pose some of the greatest current threats to island fox survival. This project could provide valuable insight into which island fox subspecies have the greatest genetic vulnerabilities and help inform conservation measures.

Another important element of Schoenberger’s project is that it integrates directly into the current protocols for health checks. Biologists are currently in the field across the Channel Islands counting island foxes, providing health checks, and administering vaccinations. As part of the 2024 health checks, some individual island foxes will provide a blood sample for transcriptomics. Schoenberger’s genetic study will compliment and build on the individual island fox data currently being collected on diet, microbiome, territory, and health.

Schoenberger was able to travel out to Santa Rosa Island and engage with the National Park biologists as they took samples. She also met individual island foxes that will be part of her investigation.

At USC, Schoenberger explains that she puts the blood samples through a centrifuge “to separate RNA from other particles.”

The samples then go through a chemical processing to isolate and purify the RNA for sequencing.

Schoenberger says: “Transcriptomics can allow insights into gene expression patterns that underlie population health and disease by providing molecular-level understanding of island fox physiology and how they function and respond to differing environmental conditions.” Friends of the Island Fox is thrilled to support Kimberly Schoenberger’s research which will provide a baseline on the differences between populations and “shed light on key genes that are affected by environmental differences and may be crucial for adaptation and survival of the island fox.”

Your donations make this research possible.

photo courtesy of P Bronstein